Attachment plug



Sept. 20, 1938. A. E. GRANT ATTACHMENT PLUG I 2 Shets-Sheet 1 Filed June 29, 1936 ATTORNEY Sept. 20, 1938. GRANT 2,130,424

ATTACHMENT PLUG Filed June 29, 19 36 2 Sheets-Sheet 2 0 20 53 f) I? l 15 INVENTOR lb erf .firanf ATTORNEY Patented Sept. 20, 1938 UNITED STATES ATTACHMENT PLUG Albert E. Grant, New York; N. Y., assignor to Albert T. Otto & Sons, 1110., New York, N. Y.

Application June 29.1936. Serial No. 87.879

6 Claims.

My invention relates to the male elements of electrical coupling devices of the type .commonly known as attachment plugs, end plugs, or connector caps. Such devices are commonly carried on the ends of extension cords and comprise an insulating cap or body and a pair of spaced metal contact blades or prongs to which the extension cord wires are connected. More particularly my invention relates to the metal conducting parts an of such devices.

Male plugs of the character here dealt with are sold in large quantities at low prices and, commercial competition being keen, inferior devices have become common in which the insulating material is of comparatively low dielectric strength and the metal parts are formed of steel or other fast rusting metal of comparatively low conductivity rather than the. more expensive and highly desirable brass. The specifications which the manufacturer is ordinarily required to meet demand that the blades or prongs comprise conducting metal of approximately one-sixteenth inch thickness in order that they will have the necessary strength and stiffness to maintain their position and alignment, such requirements being directed to the mechanical efficiency of the device.

Such weight of blade material is not necessary Y for electrical efliciency because, as will be readily understood, the current load carried by the conto tact blades can be no greater than the capacity of the comparatively light wires of the extension cord.

It is a principal object of my invention therefore to provide an end plug having improved as blades or prongs so formed as to obtain greatly increased strength and stifiness, thereby permitting the use of blade metal of lighter gauge than has heretofore been practicable, and making it possible to produce a device oi the highest quality at reduced cost.

The blade or prong members of end plugs are usually formed with foot portions whereby they are attached to the insulating housing or cap, the foot portions comprising flanges integral with the projecting portions of the blades and provided with means whereby the ends of the exto provide in an end plug a contact blade or prong member having an integral flanged foot portion in which the bend defining the foot portion is sturdily reinforced to stiffen and strengthen the construction and to insure that the prong will remain inalignment in use and will not be subject to bending and breaking. Other and further objects will appear from the following specification. 7

Referring to the drawings which form a part 10 of this specification: Figure 1 is an elevational view, partly in section, showing an end plug embodying the features of my invention in coupled relation with a standard receptacle plug member. 15

Figure 2 is an inverted plan view of the male member embodying my invention.

Figure 3 is a perspective view ofmy improved blade or prong.

Figure 4 is an elevational view, partly in section, showing a modified embodiment of my invention.

Figure 5 is a perspective view of the prong member shown in Figure 4. s.

Figure 6 is aview similar to Figure 1 showing 25 my improved end plug in coupled relation with a standard receptacle having contacts located adjacent to the inner walls of the sockets.

The device comprises an insulating body or cap l0 having a central wire passage therethru 80 at H, the face of the cap being recessed intermediate its margins at l2. A pair of plug-in contact members "-44 are secured to the recessed portion of the cap on opposite sides of the central wire passage Ii by means of studs or staples 20-20 which extend through the flanged foot portions l8 0! the members and into the walls of the cap. A binding terminal 2| is threaded through each of the foot portions and extends into a recessin the cap formed to 3 receive it.

The contact members are formed from iiat metal by means of progressive dies adapted to form a deep reinforcing channel I! in the prong or blade portions I5 over the greater part of 45 their area intermediate their edge margins and the bends at It, the opposite face of each blade having a corresponding rib embossed thereon at ll i The reinforcement of the blades thus provided imparts to them great stifiness and the overall blade thickness from the outer surface of the rib to the inner face of the-blade is at least double the thicknessof the metal from which the contact member is formed. The entering ends of the 5 blades being unchanneled, however, have only the thickness of the metal stock and are readily inserted in the socket apertures 36 of a standard convenience outlet or a receptacle plug member such as 35.

This construction permits the use of very light gauged conducting metal having thickness'only one-half or even one-third that ordinarily required in devices of this type, the saving in the material employed permitting the use of the highest grade of brass without increasing the cost above that of the cheapest steel prongs.

As shown, an opening is formed through the embossed portion of each blade at 30 for engagement by the usual protuberances 4| formed on the contact members 40 of female receptacles,

. generally, where such female contacts are positionedagainst the outer walls of the receptacle sockets. Where the female contacts are located adjacent the inner walls of the sockets, as at -.40 in Figure 6, their protuberances will be faced outwardly and will be engaged by the shoulders 3| deflned at the lower end of the channel adjacent the opening 30.

To further strengthen and stiffen the structure, particularly where the lighter metal is employed, an angular flange 33 is formed in the angle defined by the bend. l9 dividing the prong and foot portions of the device. This bracket-like flange is readily formed by swaging the metal at the time the bend I9 is imparted to it and braces the blade most efliciently, holding it at all times in accurate alignment perpendicular to the foot portions and overcoming any tendency for the blade to bend or break at or adjacent the bend.

The modification shown in Figures 4 and 5 embodies blades having the same structural'characteristics as the blades described in Figures 1 to 3 and in addition illustrates the blade tips 5!] reduced in width, extended in length, and bent back upon themselves to reinforce the structure.

at that point and to provide shoulders 5l-5l defined by the inwardly turned blade ends, such shoulders being adapted for engagement under the protuberances ll of receptacle contact members 40' (indicated in broken line in Figure 4) where such members are located adjacent th inner walls of the socket openings.

Having thus described my invention, I claim: 1. An attachment plug comprising an insulating body having a central wire passage therethru, conducting members carried by the body on opposite sides of said passage, said members each.

comprising a strip of fiat conducting metal transversely bent to deflne a foot portion whereby the member is attached to the body and a prong i portion projecting perpendicularly from the foot portion, said members each having an angular flange integral with a side edge thereof in the corner defined between said foot and prong portions to brace the members at and adjacent the bends therein, each of said prong portions being stamped intermediate its margins to provide a longitudinal reinforcing rib on one face and a corresponding channel on the other face thereof, and wire binding terminals carried by. each of said members.

thereon extending over the greater portion of its contacting area, and means carried by the foot I portion for connecting a wire thereto.

3. A plug-in contact member for an attachment plug comprising fiat conducting metal transversely bent to define a foot portion and a prong portion perpendicular to said foot portion,

" said member having an angular flange integral with a side edge thereof in the corner defined between said foot and prong portions whereby the member is braced at and adjacent the bend therein, and means carried by the foot portion for connecting a wire thereto.

4. An attachment plug comprising a housing of insulating material having a wire passage therethrough and a pair of contact blades projectlng therefrom, each of said blades comprising a straight strip of flat conducting metal less than one-sixteenth inch in thickness having a longitudinally extending reenforcing rib embossed on one face and a corresponding channel in the opposite face thereof, said channel extending over the greater portion of the projecting area of the blade and terminating adjacent the free end of the blade to form a shoulder positioned for engagement with the usual protuberances carried by the contact elements of standard receptacles.

5. A plug-in contact member for.an attachment plug comprising a thin strip of flat, conducting metal having a longitudinal stiffening rib embossed on one face and a corresponding channel in the opposite face thereof, the end portion of the strip being of less width than said rib and reversely bent into said channel, the end edge of the strip terminating to form a transverse shoulder positioned for engagement by the usual protuberance carried by the contact element of a standard receptacle.

6. A plug-in contact member for an attachment plug comprising a thin strip of flat conducting metal transversely bent to define a foot, and 2. prong perpendicular to said foot, said member having an angular flange integral with a side edge thereof in the corner defined between said foot and prong whereby the member is braced adjacent the bend therein, said prong havinga longitudinal stiffening rib embossed on one face and a corresponding channel in the opposite face" 

